Deduplicate bacon invocation

Surprising how much this thrashed so far.

Guardfile

@@ -10,7 +10,7 @@ module ::Guard
 
     def run_spec(path)
       if File.exists?(path)
-        cmd = "bundle exec bacon -Ilib/pry/test -Ispec -q #{path}"
+        cmd = "rake spec run=#{path}"
         puts cmd
         @success &&= system cmd
         puts

Rakefile

@@ -48,7 +48,12 @@ task :default => [:test]
 desc "Run tests"
 task :test do
   check_dependencies unless ENV['SKIP_DEP_CHECK']
-  all_specs = Dir['spec/**/*_spec.rb']
+  all_specs =
+    if explicit_list = ENV['run']
+      explicit_list.split(',')
+    else
+      Dir['spec/**/*_spec.rb']
+    end
   all_specs.shuffle! if all_specs.respond_to? :shuffle!
   system "bacon -Ispec -rubygems -q #{all_specs.join ' '}"
 end